16 replies to this topic

[TimberRock]

I have just started using a ZWO ASI2600MC camera with a TV NP127is. I realize a number of forum discussions have addressed this topic but I have not found what I need as far as reasonable times coupled with a reasonable number of subs for DSOs. 
 

when I use Sharpcap or NINA to calculate the exposure times, they are very short times which would necessitate many subs. Well, at around 50mb per sub, the disk space and computing power is something I never experienced with a DSLR.  With a DSLR, 300s exposure times was typical and I could easily handle up to 50 subs. I really don’t want to purchase a new computer just for this. 
 

In the experience of members of the group, would 300s sub exposure times with ZWO be something that would achieve reasonable results?  I am waiting for cloudless nights to try this out but in the meantime I thought I would ask the forum for any advice they could give. 

[alphatripleplus]

If you are doing EAA by livestacking in SharpCap, you don't have to save individual subs if you don't want to. Some people like to save individual subs for later experimentation, but many of us just save the livestacked final capture when doing EAA. Just configure SharpCap to not save individual subs.

 

If you only save the livestacked final EAA capture, rather than individual subs, your storage requirements, even with a large sensor camera like the 2600MC, will not be onerous.

 

Of course, if want to pursue AP and not just EAA, then saving individual subs would be needed.

[Meies]

As alpha said, in EAA people generally stack on the fly without saving individual subs. So at any given time, you are only storing the stacked file plus whatever overhead is needed to accomplish the stack.

Long or short subs depends primarily on whether you guide, and how long you can guide without smearing your stars.

People here frequently use lots of short subs, say, 60 x 10" (10 minutes total) so that they don't need guiding. I gravitate to fewer, long subs with guiding, say 10 x 60". But that doesn't affect storage space--it's still one frame's worth of data.

Edited by Meies, 01 June 2023 - 01:24 PM.

[TimberRock]

Does 10 minutes worth of data with an ASI2600mc produce the same or better results than, say, 10 X 10 minutes with a DSLR at ISO 800?  Also, I am more interested in AP than EAA. I think I can handle storage issues using SSD storage on a mini PC connected to the ZWO. The biggest problem I see is a computer capable of processing the data. SSD is rather inexpensive but a capable computer is another issue. 

[alphatripleplus]

Does 10 minutes worth of data with an ASI2600mc produce the same or better results than, say, 10 X 10 minutes with a DSLR at ISO 800?  Also, I am more interested in AP than EAA.

As the OP is more interested in AP, moving this topic to Beginning Deep Sky Imaging for a better fit.

[Mark Lovik]

If you care about EAA - 5 minute exposures are not very interactive.

I have a 2600 camera and typically use 10-15 second subs.  

• yes - this is a large amount of data
• post processing this later with AP tools can be really really slow
• replaying stacks in SharpCap - learning or just reprocessing for yourself is actually fast for these large subs.  Just make sure you have a good chunk or RAM on your EAA computer.
• these exposures are great for EAA - good interaction and feedback at the scope.  You are building and processing the image realtime during live stacking.
• I choose to save my subs on fast electronic storage - at least for a few weeks.

There are other huge advantages to short subs for EAA.  It's a different mindset and workflow.

Edited by Mark Lovik, 02 June 2023 - 10:25 AM.

[FrostByte]

Which DSLR were you using previously? I just picked up an ASI2600MC as well, and coming from a Canon 600D, ISO 800, subframes of the same target for the same exposure time are MUCH darker on the 2600. And I definitely agree, the storage requirements are quite painful... I haven't done any calculations yet, but I expect that I'll actually use longer subs with the 2600 than with the Canon DSLR due to the much larger DR of the astro camera.

[Sheridan]

Does 10 minutes worth of data with an ASI2600mc produce the same or better results than, say, 10 X 10 minutes with a DSLR at ISO 800?  Also, I am more interested in AP than EAA. I think I can handle storage issues using SSD storage on a mini PC connected to the ZWO. The biggest problem I see is a computer capable of processing the data. SSD is rather inexpensive but a capable computer is another issue. 

The 2600 is definitely more sensitive than a DSLR. I run my 2600 clone on a mini pc with 16gb ram 1tb ssd.  Processing will be up to the individual computer. Obviously you would want one with a decent amount of ram and a ssd as the through put would be higher.  Processing power will be the factor,  it could take a few hours to 10s of hours but eventually it should complete.
 

[unimatrix0]

It really comes down to what telescope you use (what's the F ratio); how light polluted your sky is; what filters- if any- used.  

 

Take a 15/30/60/120 shot at gain 100 and watch the histogram.

You want the histogram tight to the left and gradually dropping towards the right. I literally go by that, when I test various filters on my camera.

 

Short tailed histogram is somewhat under exposed but still good if you take many, stretched apart "hill" histogram that thick across the histogram meter is over exposed. Better be either under exposed or exposed right instead of over exposed. 

 

Study this from John Rista, excellent guide, I keep revisiting: 
https://jonrista.com...and-histograms/

[Spaceman 56]

 would 300s sub exposure times with ZWO be something that would achieve reasonable results? 

I shoot 60 seconds generally with my 2600MC and an 80mm F/7 OTA.

 

at 60 second I get small amounts of clipping, and think I could shoot 90 seconds but that would be it.

there is no benefit from clipping stars, and much to lose, so why go there ?

 

a very technical type person did the maths for me, and said 60 seconds was good.  

 

note I am shooting Broadband, and Narrowband will be different.

Edited by Spaceman 56, 03 June 2023 - 01:34 AM.

[TimberRock]

I ran some tests on stacking a large number of 50mB files from an ASI2600mc with a iMac M1with 8GB memory.  Siril will only stack 300 subs if FITS compression is used.  The time to stack them was about 21 minutes. I consider this a success and therefore an exposure time of 60 seconds is reasonable as 300 subs will give a total integration time of 300 minutes or 5 hours.  I will consider 15/30/60/120 second times for clipping when the clouds go away.  Thanks all for your input.

[NoDarkSkies]

I found 60 Seconds for items like star clusters and 180 for the rest.

With items like M42 I shoot 30 Second and 180 Seconds.

[F.Meiresonne]

Stacking can be a taxing job. Especially for somebody who uses PI..I am wondering about stacking times too if i should ever move to an astro cam, considering the subs are just way bigger then a .CR2 canon file on a DSLR.

I always try to be a bit ahead of issues, so recently i upgraded my ryzen 5 3600 to a ryzen 9 5900x. Since the prices dropped it just seemed reasonable..it cuts my stacking times in PI in half...

[Robert7980]

These are all 300 seconds, some are the mono version which would be equivalent to a little longer on the OSC… If your skies and guiding support it 300 isn’t too long for the 2600s dynamic range… Anywhere from 30 to 300 is a pretty safe zone… I usually never go below 60 though and 300 is typically my goto… You can control the stars a little easier at 120… My goal is to shoot long enough while not causing major problems and reduce the number of subs, it’s a real thing with the 2600 your data volume balloons quickly with it… If you get a string of clear nights you can rip through a couple terabytes pretty rapidly… 

 

These are f/6 and f/8 so if you’re way faster then you might need to back off some… To me 300 is a sweet spot for the sensor, I almost never have severe issues shooting that… 

 

 

Edited by Robert7980, 07 June 2023 - 08:23 PM.

[TimberRock]

These are all 300 seconds, some are the mono version which would be equivalent to a little longer on the OSC… If your skies and guiding support it 300 isn’t too long for the 2600s dynamic range… Anywhere from 30 to 300 is a pretty safe zone… I usually never go below 60 though and 300 is typically my goto… You can control the stars a little easier at 120… My goal is to shoot long enough while not causing major problems and reduce the number of subs, it’s a real thing with the 2600 your data volume balloons quickly with it… If you get a string of clear nights you can rip through a couple terabytes pretty rapidly… 

 

These are f/6 and f/8 so if you’re way faster then you might need to back off some… To me 300 is a sweet spot for the sensor, I almost never have severe issues shooting that… 

 

 

 

I did not know you could set the f/# on the ASI 2500mc.  I have only had this camera for a short while with little exposure time.  Am I missing something?

 

BTW, your stacks look good.

 

Paul

Edited by TimberRock, 08 June 2023 - 06:04 PM.

[idclimber]

I did not know you could set the f/# on the ASI 2500mc.  I have only had this camera for a short while with little exposure time.  Am I missing something?

 

BTW, your stacks look good.

 

Paul

Focal ratio is not adjusted by the camera.Focal rio is simply the ratio between the aperture to the focal length. The way this is adjusted with some refractors is by using a reducer or simply a flattener. This changes the focal length and as such the focal ratio.

[TimberRock]

Focal ratio is not adjusted by the camera.Focal rio is simply the ratio between the aperture to the focal length. The way this is adjusted with some refractors is by using a reducer or simply a flattener. This changes the focal length and as such the focal ratio.

Gotcha!